K series click

[Colin Mill]

Tony

 

It could be so. I'm not convinced about the argument against insulation - if you have to crank the thing for so long that the solenoid cooks itself you have other problems! An Ali shield with a free flow of air behind it would, I think, be better anyway. I thought the problem affected the magnetti starters as well as the magneton ones. Am I right?

 

Colin

 

[Paulo]

Colin,

 

I don't think that it's the cranking that does the cooking.

It's just that there is so much heat, from the exhaust headers and the motor, that once the Starter (solenoid) is hot it remains hot.

 

There are probably two factors that reduce the efficiency of the solenoid, the differential expansion rates (badly toleranced parts) and the increased resistance.

 

It must be said that I didn't experience this problem until I changed the exhaust system (421 SLR) and started doing track days. The standard system ( 4 into 1 under the bonnet) worked all last summer which down here was very,very hot.

 

Paul

 

[Adam]

Not sure if this helps anyone understand the starter/solenoid problems, but...

 

My solenoid/starter (2001 1.8K SS model) has four connections;

a- the +ve feed (fat red cable) from the battery (or iso switch)

b- the switched +ve feed into the starter motor

c- the +ve feed into the solenoid, thin brown/red feed from starter button/relay etc

d- the chassis ground (with the earth strap)

 

The solenoid is connected to b/c and the starter motor b/d. What this means is that the solenoids earth path is via the starter motors winging, and once it has fully engaged, it will connect "a" to "b" and therefore also short its own "earth" path to +ve. This was news to me ... but I imagine that once the starter is spinning, that it "holds" itself in the extended position to make contact with the flywheel. It also means that if one of the starter motors coils is burnt out or there is any dirt on the commutator (correct term? copper pads with bushes on inside starter), then the solenoid can "lose" its earth path and not be able to energise....

 

Chris W - if youre reading this, maybe you could correct me or confirm this is right?

 

 

Edited by - Adam on 31 Jul 2004 01:07:32

[Colin Mill]

Hi Adam

 

I think the negative end of the solenoid could be grounded internally to the case.

 

Colin

[Adam]

Colin, thats what I was expecting to find ... but in my case its as described in my previous post.

[Colin Mill]

Adam

 

Is it possible that the switched feed to the solenoid (brown/Red wire) is a switched earth - even this would be a bit strange as you would expect the solenoid to run between an unswitched positive and switched negative.

 

With the thing wired up and working as yours is I would expect the solenoid to energise ok because its resistance is a lot less than the starter. This could be good as the solenoid current also going through the starter helps spin the starter to find a mesh with the ring gear. However, once it pulls in, its own contacts effectively bypass the coil. It would immediately drop out unless the friction etc on the starter holds it in. This would mean that letting go of the key would not stop the starter unless the engine fires and offloads it!? It would crank a dead engine till the battery died while you sat and listened to it with your arms folded. All very oddball - no wonder there are problems.

 

Colin

 

 

[Adam]

Colin, I see what u mean. I must have got it wrong. Ill check it out again if I ever need to remove the starter ...

 

Edited by - Adam on 31 Jul 2004 15:05:43

[Colin Mill]

Adam

I'm kicking myself for not taking a much closer look at it before I dropped the engine in a couple of weeks back. I just thought at the time that it looked suitable for a 250cc bike engine not a car. Do you know what size engine the thing is designed to crank?

 

Colin

[Adam]

Colin, the starter I have looks like the one on the CC web site. I think its the 1KW non-race version, possible a "Magnetti Marelli" geared one?? (soleniod on the bottom)

 

I dont know what other cars its used in .... someone mention Skoda in one of the other posts on here. Theres also been mention of a race version at 1.4KW. I imagine theres some relationship between starter motor power and engine size/CR etc that it can turn - but I dont know it.

 

 

 

[F355GTS]

Adam/ Colin

 

The swithced feed to the starter is a 12v + feed, It provides an energy feed to the solenoid which when charged forces the piston backwards resulting in two actions, it engages the starter gear with the flywheel and connects two contacts at the back of the solenoid in effect joining the big red wire from your battery or master switch to the short wire connection from the solenoid to starter motor. The solenoid and starter motor are earthed through the case

 

Mark

[Gerry Simpson]

I had the same problem, it was the solidoid, it had melted under the attentions of the exhaust system and the windings had got a short.

 

Sometimes it did, and then sometimes it didn't. Then mostly it didn't. The car always started with a push.

 

Sent it off to nice man a Brise, bingo now it always does, and I'm 90 quid lighter, but happy.

[Adam]

Ok Mark/Colin

 

The starter failed again today, so out it came yet again.

 

In my case; the solenoid is wired in series with the stater, ie as my first posting.

This seems very strange at first, but it works (well, it did for 3 years on my car).

The reason why I think this works is;

the initial voltage across the solenoid is 10V {12V x 0.250ohm/0.300ohm)

but then the "holding" voltage across the solenoid falls to 2.5V AC with a 1V DC offset once the starter is running(I measured this with the start running on the bench).

 

The problem with my starter, or rather the solenoid, appears to be that the "solid armature" often gets stuck bbefore the starter contacts are closed. Im still not sure if its the alignment with the flywheel or internal to the solenoid though.

 

For the "record" here are a few measurements I took;

resistance of solenoid 0.250 ohm (0.500V/2A)

resistance of starter 0.050 ohm (0.105V/2A)

resistance of main contacts (the two main contacts on the back of the solenoid) 0.001ohm (0.003V/3A)

These were measured by passing a limited current (3A) through the load, and measuring the voltage across it.. so not exactly the same as when the starter is spinning etc, but still give an idea of sensitivity of the system to small resistances in it supply path.

 

 

Edited by - Adam on 1 Aug 2004 02:44:42

[bonzz]

Try putting some steel washers 2-3mm thick on the securing bolts, between the starter motor and the bellhousing. this worked for my car which has the bog standard starter motor. Sorted!

[Adam]

Thanks bon - Ill give it try..

 

Found this on the hold/pull function of a solenoid.

http://www.hondahookup.com/manuals/Starter.pdf

Seems that in some designs there are two coils within the soleniod - not sure if this applies to the various caterham ones though.